Schoeps M 221B
A miniature tube condenser with a mechanical pattern switch, a Grosskopf delay ring, and a sound that still turns up on Telarc's best-loved chamber recordings.
Overview
The M 221B is the amplifier half of a two-part system. Pair it with the M 934B capsule and you have a miniature dual-pattern tube condenser built around the AC701k, the same subminiature tube found in Neumann's SM2 and SM69 stereo microphones. As documented in Mix (February 1982, p.44), studios of the era routinely stocked microphones from Wright, Neumann, and other makers alongside parametric equalizers and dbx compressors in their outboard racks. The model number tells you what you're looking at - the first part designates the amplifier, the second the capsule. The M 221B/M 934B combination was manufactured from the late Fifties until the end of the Sixties, reportedly spanning 1958 or 1959 through 1968 or 1969 according to the serial-number ranges logged in a 1985 recording-engineering survey.
The pattern switching is what makes this microphone unusual. Most dual-pattern condensers switch electrically. This one changed between omnidirectional and cardioid mechanically, using a 1952 Grosskopf design: a special plastic ring that screwed onto the end of the capsule. The ring formed part of the acoustical delay network that produced the cardioid pattern. So the polar response is set by a piece of plastic threaded onto the front of the capsule. It's the detail that most distinguishes the M 221B from its descendants.
Physically, the microphone is small and unobtrusive. Its shape, 20mm (0.8-inch) diameter, and general dimensions are very similar to the solid-state Schoeps microphones still manufactured today, and the design dates to the 1950s. The tube amplifier is rated at 200 ohms nominal source impedance with a recommended load of 1,000 ohms nominal, and it wants roughly 40 dB of console gain. Those are modest figures, which fits the AC701k's civilized output.
Sonically, the M 221B/M 934B has a reputation for cleanliness. A 1985 subjective evaluation published in Recording-Engineer placed it alongside the Neumann U47 - both received a rating of 8 - while noting that the two microphones could hardly be less alike otherwise. The Schoeps was described as small and unobtrusive, like its present-day FET descendants, with a clean, crisp quality and some high-frequency emphasis. The U47, by contrast, was characterized as large and imposing, with a lower and more pronounced response peak that gives it a very personal, up-front sound. The evaluation's conclusion was pointed: the U47 commands enormous respect, but it will not appeal to engineers seeking accuracy, whereas the Schoeps' high-frequency lift was judged enhancing rather than hard-edged.
The same evaluation ranked the M 221B/M 934B in the middle of a field of fifteen microphones, with a composite score of 6.66 against a control pair of Neumann TLM170s that scored 7.79 in that session. It finished below the U47 (6.74), the AKG C24 (6.68), and the C414EB/P48 (6.86), and above the Milab VIP-50 (6.55). Read those numbers carefully. The panel was evaluating a tube microphone from the late Fifties against FET designs from the mid-Eighties.
The M 221B/M 934B earned its lasting reputation in the recording studio, specifically in the hands of Telarc's Jack Renner. The Cleveland Quartet's recording of Schubert's "Trout" Quintet and Quartet in A Minor - performed on a matched set of Stradivarius instruments made between 1696 and 1736 - was captured on Schoeps M221B tube microphones.
The M 221B was never a high-volume product, and the amplifier and capsule are separate components. Finding a complete, matched M 221B/M 934B with its original screw-on pattern ring is considerably harder than finding either piece alone. The AC701k tube is the other long-term concern. It is a subminiature tube used across a generation of German broadcast microphones, and while it is not impossible to source, it is not something an owner picks up at the local electronics shop. Buyers should expect to verify tube condition and, ideally, confirm that the pattern ring is present and undamaged. It is the microphone's signature design feature and a small, easily lost piece of plastic.
Late in production, the Schoeps factory announced that enough parts remained to manufacture twenty final M221B/M934C microphones. These were to be identical to the review microphones then in circulation, with one exception: the absence of the screw-on capsule ring, hence the "C" designation. So a microphone whose cardioid pattern depended on a threaded plastic ring finished its run with twenty units that could not do cardioid at all.
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